Really enjoyed the concept of figuring out where the tunnel was.
The Main menu animation, buttons and overall feel of the game was very well done. The tutorial explained the rules of the game very well made. I liked how you could transition into the game after the tutorial.
The music was well made! I liked how it varied from the in-game and the tutorial. In-game music gave it a detective feel to it. As if I was a detective figuring out the case of the mysterious tunnel.
Having two different phases was a nice touch.
Some Remarks:
It might have been better to have the block's number displayed next to it in the map instead of clicking it. I feel this would help in quickly seeing where they are going, instead of having to memorize everything.
Maybe have some shortcut keys to: Investigate, watch list and arrest, to avoid having to drag the mouse back and forth from the map and onto the interaction panel.
This might have been me, but I felt that more tools for the detective would help a lot, as it is quite difficult to gauge what exactly is happening with a lot of people moving about (like I said, could be just me). Something like restricting an area for a certain amount of time. Something that maybe could help me isolate a suspicious section of the city.
I don't know if it was intentional, but having icon textures when investigating might help gain a better idea of what they carry, instead of dragging your mouse. This would help save time as time is precious!
Overall, I really enjoyed playing the game. It was fun being a detective, even though I failed to find the tunnel.